1. Field of the Invention
This invention relates to an improved treatment of diseased or occluded vascular grafts in patients having undergone coronary artery bypass surgery.
2. Description of the Related Art
Coronary artery disease is a major problem in the U.S. and throughout the world. Coronary arteries as well as other blood vessels frequently become clogged with plaque, which at the very least impairs the efficiency of the heart""s pumping action, and can lead to heart attack and death. In some cases, these arteries can be unblocked through noninvasive techniques such as balloon angioplasty. In more difficult cases, a bypass of the blocked vessel is necessary.
In a bypass operation, one or more venous segments are inserted between the aorta and the coronary artery. The inserted venous segments or transplants act as a bypass of the blocked portion of the coronary artery and thus provide for a free or unobstructed flow of blood to the heart. More than 500,000 bypass procedures are performed in the U.S. every year.
Such coronary artery bypass surgery, however, is a very intrusive procedure that is expensive, time-consuming and traumatic to the patient. The operation requires an incision through the patient""s sternum (sternotomy), and that the patient be placed on a bypass pump so that the heart can be operated on while not beating. A saphenous vein graft is harvested from the patient""s leg, another highly invasive procedure, and a delicate surgical procedure is required to piece the bypass graft to the coronary artery (anastomosis). Hospital stays subsequent to the surgery and convalescence are prolonged.
Over time, the vein graft itself may become diseased, stenosed, or occluded, similar to the original bypassed vessel. Old, diffusely diseased saphenous vein grafts are considered contraindications for angioplasty and atherectomy, severely limiting the options for minimally invasive treatment. Some diseased or occluded saphenous vein grafts are associated with acute ischemic syndromes, however, necessitating some form of intervention.
Thus, there is a need for an improved treatment of diseased or occluded grafts in patients having had coronary bypass surgery.
The preferred embodiments of the present invention address the need in the previous technology by providing a bypass system that restores the flow of oxygenated blood through the body. In a preferred embodiment, there is provided a method for bypassing an existing coronary artery bypass graft in a patient. A hollow conduit is inserted in the patient""s myocardium at a location distal to the site of attachment of the graft, such that the conduit allows oxygenated blood to flow from the patient""s heart directly into the coronary artery. The conduit is preferably delivered to the myocardium through the coronary artery bypass graft, to ensure that the conduit is positioned in the myocardium at a site that is distal to both the blockage in the coronary artery, and the site of attachment of the graft to the coronary artery. Locating the proper site, for example, through the left ventricle of the heart is very difficult. Thus, delivery of the conduit through the graft simultaneously solves both the problem of therapy and the problem of locating the proper site for insertion of the conduit in bypass patients.
The methods disclosed herein are preferably performed percutaneously, but other minimally invasive methods, and open-chest methods, can also be used. Prior to insertion into the patient, the conduit is preferably mounted on the distal end of a delivery catheter. The catheter is then inserted into the patient""s vasculature, into the aorta, and then into the bypass graft for delivery into the myocardium.
Another embodiment of the invention includes a method for improving the patency of a coronary artery or other arterial or venous bypass graft. A lining is inserted in the hollow interior of the graft and preferably permanently attached to the graft. The lining can be made of various biocompatible materials, but a section of vein from the patient is preferred. The lining can be mounted on an inflatable balloon catheter, such as those used in angioplasty. The distal end of the catheter is delivered to the interior of the graft, and the balloon is inflated to expand the lumen of the graft and the lining. If desired, a delivery catheter can be used to deliver the catheter bearing the lining to the site of the graft. This method improves the xe2x80x9cproximal flowxe2x80x9d through the existing graft.
The methods disclosed herein for bypassing an existing graft and for improving the patency of an existing bypass graft can be used in combination, or in the alternative.